The goals of our proposed research program are to characterize two interrelated nutritional phemonena: the patterns of nutrient choice that young and old people exhibit, and the effects of particular nutrients on behavior (and the changes in sensitivity to these effects that might occur as a result of aging). We have developed facilities for quantifying food choice and for assessing the effects of particular foods and nutrients on mood, performance, and other experimentally-analyzable behaviors. Using them we have affirmed that certain nutrients can indeed affect behavior, and we have examined the patterns of nutrient-choice, before and after drug treatments, of a particular set of subjects ("carbohydrate-craving" obese people). We now hope to obtain normative data on patterns of nutrient-choice and behavioral responses to nutrients among young and old sujbects of both sexes. Thus we will: 1. Determine each subject's patterns of daily calorie and nutrient intake (i.e., what is chosen for consumption at what time of day), and determine the extent to which these patterns vary from day to day and from person to person. 2. Determine each subject's sensitivity to various behavioral effects of carbohydrate and protein consumption. Based on earlier studies of humans and experimental animals, we anticipate observing some constancy in each subject's daily nutrient choice patterns (e.g., number of calories per day; proportions consumed at each meal and as snacks; proportions represented by carbohydrates and by proteins), - perhaps reflecting the operation of brain mechanisms that allow the individual's appetites for particular nutrients to be coupled to the neurochemical changes induced by prior meals. We also anticipate that aging, with its concomittant loss of neurons, may render people more sensitive to the behavioral effects of nutrients, and may modify the proportions of protein and carbohydrate that people choose to eat.